1. Field of Invention
This invention relates to spacer layers for an electrophoretic display device, and methods for making such spacer layer.
2. Description of Related Art
Electrophoretic displays, also more commonly referred to as electronic paper, are well known in the art. An electrophoretic display generally comprises a suspension of charged pigment particles colloidally dispersed in a liquid of matching specific gravity contained in a cell comprising two parallel and transparent conducting electrode panels. The charged particles are transported between the electrode panels under the influence of an electric field, and can therefore be made to display an image through appropriate application of the electric field on the electrodes. The advantages of electrophoretic displays as a means for providing information has been well appreciated in the prior art.
U.S. Pat. No. 4,272,596, incorporated herein by reference in its entirety, illustrates a typical electrophoretic display structure. The electrophoretic display device comprises a pair of electrodes associated so as to form a cavity therebetween, which cavity is filled with an electrophoretic suspension layer comprising a colored suspending medium containing colloidal sized particles in an electrically insulating liquid and finely divided electrophoretic particles suspended in the suspending medium. A source of electrical potential is coupled to the electrodes and with an electric field applied, the marking particles form an image as they follow the field. See especially FIG. 1 therein.
U.S. Pat. No. 3,668,106, incorporated herein by reference in its entirety, describes an electrophoretic display and/or recording device in which an electrophoretic suspension layer including a dispersion of at least one electrophoretic material in a finely divided powder form suspended in a suspending medium is interposed between a pair of electrodes. An electric field is imposed across the electrophoretic suspension layer to change the optical reflective property of the suspension layer by changing the spatial distribution of the electrophoretic material in the suspending medium electrophoretically.
One of the major issues still needing to be addressed in the field of electrophoretic displays is resolution of the images displayed. The present invention improves upon the resolution achievable with an electrophoretic display through design of a spacer layer used to form the individual cells of the display device.